Pressure control system for convergent-divergent exhaust nozzle

Abstract

A system to assist flap actuation of a convergent-divergent exhaust nozzle to overcome the high air loads on the flaps, so that the nozzle flaps can be properly positioned by the actuators. The structural members of the system are operatively associated with a controlled, air-pressurized, cavity positioned in the exhaust nozzle section. Pressurized air from the cavity acts against the flaps, and helps to overcome the load required to move them. The system is useful in any exhaust nozzle, and most particularly where the exhaust nozzle is two-dimensional, i.e., rectangularly shaped.

What is claimed is: 
     
       1. A pressure control system for a rectangular convergent-divergent exhaust nozzle of a jet aircraft turbofan engine having exhaust nozzle flaps located within the main exhaust flow, said system comprising: a. means for providing a cavity located in said exhaust nozzle adjacent one side of said exhaust nozzle flaps, wherein said means includes and said cavity is defined by constituent convergent flaps of said exhaust nozzle flaps, by a forward end of constituent divergent flaps, by constituent sealing flaps of said exhaust nozzle flaps, by a forward end of constituent external flaps of said exhaust nozzle flaps, wherein said sealing flaps interlink said divergent flaps and said external flaps, by a cross-beam-to-convergent flaps seal of said exhaust nozzle flaps, and by a side wall of said rectangular convergent-divergent exhaust nozzle; and   b. means, operably connected to said cavity, for controlling pressure within said cavity in relationship to induced loads applied to the other side of said nozzle flaps by said main exhaust flow during operation of said jet aircraft turbofan engine, wherein this pressure control means includes: (1) means, operably connected to said cavity, for conveying air into said cavity;   (2) means, operably connected to said cavity and to said main exhaust flow, for sensing pressure difference between said pressure in said cavity acting on said one side of said nozzle flaps and pressure applied to said other side of said nozzle flaps by said main exhaust flow and for providing a signal in response thereto, wherein this pressure difference sensing and signalling means includes: an air pressure sensor in said cavity; another air pressure sensor in said main exhaust flow; and, a differential air pressure sensor connected to said air pressure sensor in said cavity and to said other air pressure sensor in said main exhaust flow;   (3) means, operably connected to said air conveying means and to said cavity at a location therebetween, for controlling the pressure of air entering said cavity in response to said signal, wherein this entering air pressure control means includes a pressure control valve; and   (4) means, operably connected to said pressure control valve and to said differential air pressure sensor, for maintaining a predetermined difference between the pressure of the air in said cavity and the pressure of the air in the main exhaust flow, wherein this means includes an electronic engine control with balancing pressure logic.